There are presently available on the marketplace many forms of multibit screwdrivers where the several bits are contained within the hollow handle. When it is desired to use a particular bit, the handle is opened by unscrewing the cap for the handle and selecting the needed bit. The selected bit is then placed in the chuck at the other end of the handle for use. This system results in the loss of bits, because the bits are not retained within the screwdriver handle.
Multibit screwdrivers are available which provide in one form or another arrangements which minimize or prevent loss of the screwdriver bits. Examples of these screwdrivers are found in U.S. Pat. Nos. 512,911; 2,765,013; 3,006,395; 3,194,286; 3,405,749; 4,241,773 and 4,463,788. A variety of techniques are disclosed in these patents for selecting a desired bit from a magazine in the handle and either extending it for immediate use or moving to a position for location in a chuck to drive the bit. U.S. Pat. No. 4,463,788 includes the use of a bit selector cup rotatably mounted on the bottom portion of the handle containing the bit. The bit selector cup includes a slot of a width and length to permit withdrawal of a selected bit from the handle magazine, transverse movement of the bit end to centrally of the handle for upward insertion into the chuck contained in the bottom portion of the handle. This type of screwdriver provides for a selection of multiple bits from the handle magazine yet locates the bit centrally of the handle for ease of use. This is contrasted with the screwdriver arrangements of U.S. Pat. Nos. 512,911 and 4,241,773, which involve securing of the bits offset from the centre of the handle axis. This eccentric securing of the bits relative to the central axis of the handle provides an eccentric motion when using the screwdriver. Thus the tool can only be used for the simplest of jobs. In U.S. Pat. No. 4,241,773, the selected bit is retained in the handle by providing an enlarged bit head which will not pass through the apertures of the selector disc. In this arrangement, the enlarged head acts as a device to retain the bit in the handle. However, this arrangement does not contemplate a bit selector cup which has an elongate slot therein to provide for transfer of a selected bit from the handle magazine to the centrally located chuck of the handle. To secure the selected bit in the handle, where each channel in the handle acts simultaneously as a magazine for the bit and also as the chuck, the selector disc is spring loaded to engage a groove in the shaft of the bit to lock the bit in place. This arrangement provides for locking of a selected bit in the handle each time a bit is withdrawn. This can result in difficulties in removing and selecting another bit in operations that require several quick changes from one bit to another.
Applicants' copending application Ser. No. 681,886, filed Dec. 14, 1984, discloses an improved arrangement for the bit ends and chuck to facilitate use of the screwdriver. The screwdriver bit includes a number of operative external faces equal to or a multiple of the number of bits provided in the handle. Similarly, the chuck has a bore presenting a corresponding plurality of internal operative faces for engaging the bit end as withdrawn from the handle magazine. Such an arrangement provides for faster and easier positioning of the bit end within the chuck of the screwdriver handle.